Potentiometer



DeC. 10, 1968 Q F, KLUG ET Al.

POTENT IOMETER 3 Sheets-Sheet l Filed NOV. 4, 1966 5 N00 N E 0 P VK@ f o N, r 3/F/ my f rz. 6 4 a., 40 B 0^ F www 5M, 0 w

Dec. l0, 1968 R F, KLUG ET Ax.

POTENTIOMETER 3 Sheets-Sheet 2 Filed Nov. 4, 1966 lmp,

#Trae/Veys Dec. 10,1968 Q F, KLUG ET Al. 3,416,120

POTENTIOMETER Filed Nov. 4, 1966 3 Sheets-Sheet 3 rroPA/fvs United States Patent O 3,416,120 POTENTIOMETER Robert F. Klug and Larry B. Lindquist, Columbus, Nebr., assignors to Dale Electronics, Inc., Columbus, Nebr., a corporation of Nebraska Filed Nov. 4, 1966, Ser. No. 592,077 16 Claims. (Cl. 338-183) ABSTRACT F THE DISCLOSURE A potentiometer device having a housing having a closure cover plate and a resistance coil, lead screw and collector member extending the length of the housing. A wiper arm is carried upon said lead screw and extends between the resistance coil and the collector member. Integral terminals for the resistance coil are provided which extend through the housing and are in supporting engagement with the resistance coil at its opposite ends. The collector member is positioned along one side wall of the housing and is yieldably held in position by an opstanding wall in the housing and the cover or closure member.

The closure member is provided with ribs along its peripheral edges for engagement with the top edges of the housing and upon a limited amount of heat and pressure being applied to the housing and closure member the rib is melted to form a seal in the joint between the closure member and the housing and simultaneously as the closure member is moved into mating engagement with the housing point projections on the collector mem ber and terminal plates connected to the resistance coil are imbedded in the closure member and are forced into a press-tit engagement with the wall opposite the closure member. The terminal plates may extend through an opening in the wall opposite the closure member wherein the openings for the terminal plates are such a size that they restrict the movement of the terminal plates therethrough. The ribs along the edges of the closure wall require substantially less heat to melt the material in the ribs than would be required to melt the relatively wider edges of the closure wall and thus the sealing operation takes place in a shorter time with less temperature and heat. An adhesive may be used in the joint sealing the housing; however, the resin in the plastic material of the housing enclosure member will normally be suicient.

The lead screw includes a metal portion and a nylon head portion which is connected to the lead screw by a rib and groove molded connection. The lead screw is provided with threads of such a design that neither the wiper assembly or the threads of the lead screw will be damaged upon the lead screw being turned beyond the amount required for moving the wiper assembly between the normal limits of movement within the housing. Thus slipping between the wiper member and the lead screw will occur but will not cause damage to either component.

The resistance coil is positioned in the housing on spring portions of a pair of terminal plates. The wiper assembly is provided with a spring arm for engaging the resistance coil. Thus, the collector member and the terminal members for the resistance coil make it possible to employ various resistance coils Without redesigning these particular parts. The wiper assembly having its novel configuration also makes it possible to vary the diameter of the resistance coil and thus provide great versatility for assembling the potentiometer.

It has been found that in heating the housing and the closure member that the ribs on the closure wall serve as energy directors and are particularly responsive to the application of an ultrasonic plastic Welder. A slip t is provided between the closure wall and the housing when initially assembled such that the melted plastic material .and the rib will flow into the space between the closure wall and the housing and thus form the seal therebetween. The application of heat and pressure to the closure wall and housing result in the seal therebetween being formed but also the locking in position of the collector member and the terminal plates.

A further object of the device of this invention is to provide snap-in retaining means in one of the housing portions to releasably receive the ends of the lead screw to retain and journal the lead screw.

The preceding brief description of this invention makes it apparent that the object of this invention is to provide improvements in lead screw adjusted miniaturized potentiometers. The advantages discussed will thus be apparent to those skilled in the art. Our invention consists in the construction, arrangements, and combination, of the various parts of the device, whereby -the advantages contemplated are attained as hereinafter more fully set forth, specifically pointed out in our claims, and illustrated in the accompanying drawings, in which:

FIG. l is an exploded fragmentary perspective view of the miniaturized potentiometer drawn to an enlarged scale;

FIG. 2 is a side elevation view of the potentiometer of FIG. 1 drawn to a reduced scale;

FIG. 3 is a top plan view taken along line 3-3 in FIG. 2;

FIG. 4 is a longitudinal cross-sectional elevational view of the potentiometer taken along line 4-4 in FIG. 3;

FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. 4;

FIG. 6 is a cross-sectional view taken `along line 6 6 in FIG. 4;

FIG. 7 is a cross-sectional view taken along line 7--7 in FIG. 4;

FIG. 8 is a cross-sectional View taken along line 8 8 in FIG. 4;

FIG. 9 is a longitudinal cross-sectional elevational view of an alternate design of a miniaturized potentiometer;

FIG. l0 is a cross-sectional view taken along line 1li- 10 in FIG. 9;

FIG. ll is a side elevation view of the wiper assembly only;

FIG. 12 is an end elevation view taken along line 12 12 in FIG. 1l;

FIG. 13 is an end elevation view taken along line 13- 13 in FIG. 11;

FIG. 14 is a top plan view taken along line 14-14 in FIG. 13;

FIG. 15 is a fragmentary cross-sectional view of the housing in its sealed closed condition;

FIG. 16 is a partial sectional view of an alternate housing showing an alternate terminal clip construction; and

FIG. 17 is a partial elevation at an enlarged scale of the lead screw showing the details of the threads thereon.

. The potentiometer of this invention includes a housing unit 10 having end walls 12 and 14, side walls 16 and 18 and a top clos-ure wall 20 disposed opposite a bottom wall 22. Inside the housing, a collector member 24 is provided along with a lead screw 26 and a resistance coil 28. A wiper assembly 30 is threadably Amounted on the lead screw 26 for engagement with the collector member 24 and the resistance coil 28. An electrical terminal 32 for the collector member 24 and a pair of terminal members 34 and 36 at opposite ends Aof the resistance coil 28 extend through the bottom wall 22 of the housing 10.

The collector bar 24 is of spring material and includes an upper vertically disposed flat portion 38 integrally connected to a transversely inwardly and downwardly extending portion 40 which in turn merges into a transversely outwardly and downwardly extending portion 42. Lastly, a downwardly and vertically extending portion 44 is integrally connected to the portion 42. A pair of upwardly extending V-shaped projections 46 are provided at opposite ends of the portion 38 for engagement with the closure wall 20. The terminal portion 32 extends downwardly from the portion 44 along the lower side of the collector member 24. The terminal portion 32 is tapered along its substantial length. The collector member 24 is disposed in the housing unit 10 along the inside surface of the side wall 18 and against a retainer wall 48 having a horizontal shoulder 50 on which the bottom portion 44 of the collector member 24 rests. The retainer wall 48 is seen in FIGS. 5 and 6 for example to have a tapered surface facing the collector member 24 and the wall terminates in the middle area of the portion 42. It is seen that the space between the housing wall 18 and the retainer wall 48 is sufficient to stabilize the collector member and thus effectively hold it in place. An opening is provided in the bottom wall 22 to receive the terminal portion 32 and the opening is of such a size that the terminal is press-fitted into the opening.

The lead screw 26 has a metal threaded portion 52 with a head portion 54 of nylon material molded thereon. A rib and groove connection is provided between the head 54 and the lead screw shaft 52. A groove 56 is diametrically formed in the end of the lead screw shaft S2 and a rib is provided in the head 54 for mating engagement with thc groove. The head 54 is preferably molded onto the shaft 52 and the groove 56 prevents rotation by the head 54 on the shaft 52. A diametrically located slot 60 is provided in the outer end of the head 54 for receiving a screw driver in rotatably adjusting the lead screw. An annular shoulder 62 formed on the head 54 is positoned in an semi-cylindrical recess 64 adjacent a shoulder 66 in the housing unit 10 adjacent the end wall 12. Thus the lead screw is permitted to rotate in place without any relative longitudinal movement.

The opposite end of the lead screw is received in a semi-cylindrical recess 68. The detailed construction of recesses 68 are best shown in FIGS. 6 and 15. The recesses 68 are substantially circular in cross-sectional shape, but are open at their upper portions as dened by tapered projections 68A. The lateral distance between the inner points of projections 68A is less than the diameter of the circular recesses 68, and is also less than the diameter of shaft 52. As a consequence, the shaft 52 can be forcibly snapped into the recesses 68 as the slightly resilient projections 68A are momentarily deformed, whereupon the ends of shaft 52 are rotatably journaled in the recesses 68. The cover all is provided with mating openings 70 and 72 at its opposite ends for receiving the lead screw head 54 and the opposite ends of the shaft 52 as is seen for example in FIG. 1.

The wiper assembly mounted on the lead screw 26 includes a pair of vertically spaced apart arcuate shaped portions`74 and 76 with threads 78 and an integral U- shaped portion 80 extending transversely of the lead screw for engaging the collector member along the portion (FIGS. 5 and 6). Electrical contact is made between the wiper member 30 and the resistance coil 28 through a portion 82 extending transversely outwardly and downwardly from the arcuate portion 76. A protuberance 84 is provided on the end of the portion 82 for enhancing the electrical contact with the resistance coil 28. Should the lead screw 26 be adjusted to an extent that the wiper assembly would engage the inner ends of the lhousing 10, the wiper assembly and lead screw are protected against damage from further rotation of the lead screw. This is accomplished by the springing apart of portions 74 and 76 as threads 78 on the wiper assembly ride over the arcuate threads (FIG. 17) 52A of lead screw 26.

It is seen in FIG. 6, for example, that the lead screw 52 is disposed in the housing unit 10 above the resistance coil 28 and between the resistance coil and the collector member 24.

The wiper member 30 is limited against rotational movement by its portion engaging the portion 40 of the collector member and the protuberance 84 on arm portion 82 engaging the resistance coil 28.

As also seen in FIG. 6, for example, the resistance coil 28 is held against rotation and is yieldably supported by semi-circular portions 86 extending transversely inwardly from the terminal members 34 and 36. The portions 86 terminate in outwardly flared ends 88. Protuberances 90 are formed on the inside surface of the semi-circular portion 86 for locking engagement with the resistance coil 28.

The terminal members 34 are also provided with upstanding flat portions 92 having V-shaped pointed projections 93 on their upper ends for engagement with the cove-r plate 20. In FIG. 7 it is seen that the upstanding portion 92 is positioned flat against the inside surface of the housing wall 16. In the same plane with the portion 92 is a downwardly extending V-shaped tapered terminal portion 94 which extends through a slot 96 formed in the housing (FIG. 1) and having a width the same as the width of the terminal portion 94 so that it is press-fitted into the opening or slot 96.

The `cover plate 20 is provided on its inner surface with V-shaped downwardly extending ribs adjacent its end and side edges for engagement with longitudinally extending shoulder 102 formed inwardly in the top portions of the housing walls. Upstanding side wall portions 104 extend along the outer longitudinal edges of the cover all 20. When the housing is initially assembled the projections 93 on the terminal members 34 and 36 and the projections 46 on the collector member 24 also engage the bottom side of the cover plate 20. At this point, the terminal portions 32 and 94 are nested in their respective openings in the housing 10. Then, preferably heat is applied in the area of the ribs 100 thus melting them and lli-ng the space 103. Heat is preferably applied through ultrasonic welding wherein ultrasonic vibrations are imposed on the housing while pressure is exerted on the housing to force the cover plate 20 downwardly on the top edges .of the Ihousing side and end walls. It is also seen that the cover plate 20 is pressed into the housing 10 as the ribs 100 melt and may slightly fill the space 103. The bond line is best defined in the area of rib 100. The V-shaped rib 100 :directs the energy to the point of the rib and the point of the rib is the point of greatest heat concentration as the ultrasonic vibrations are imposed on the housing. This movement and the softening of the cover plate 20 permits the projections 46 and 93 to become imbedded in the plate 20. The pressure of the plate 20 against the projections also press-lits the terminal portions 32 and 94 into their respective openings. Upon the cooling and hardening of the joint between the cover plate 20 and the housing unit 10, the components therein are fixed in place by the cover plate 20 since the projections 46 and 93 are locked to the cover plate. In FIG. 15 a bead of plastic material from the ribs 100 is shown lling the clearance space 102 between the cover plate 20 and the housing side walls 16 and 18.

FIGS. 9 through 14 illustrate an alternate embodiment of this invention wherein all components but the wiper member are similar to those hereinabove described. The wiper assembly is referred to generally by the reference numeral 112 and is seen to be U-shaped with a bight portion 114 having a pair of leg portions 116 and 118. The bottom ends of each of the leg portions 116 and 118 are provided with protuberances 120 which engage the portion 42 of the collector plate member 24 and the resistance coil 28 respectively.

A pair of clamping lingers 124 semi-circular in shape are deformed out of the leg portions 116 and 118 to extend around the lead screw portion 52. Inwardly extending protuberances 126 are provided for engaging the threads of the lead screw portion 52. It is thus seen from FIG. for example that the legsl 116 and 118 are spring biased into engagement with the collector member 42 and the resistance coil 28 and accordingly will maintain contact throughout movement along the entire length of the lead screw 26.

An alternate clip 128 is used in conjunction with the wiper assembly 112 of FIG. l0, and is comprised of a vertical leg 130 which is tapered -at its lower end as are the lower portions 94 of clips 34 and 36. The upper portion of leg 130 is then bent back upon itself to form arm 132 which extends downwardly and inwardly to terminate in an arcuate portion 134 with a lip 88 and protuberances 90A similar to the lip 88 and protuberances 90, respectively, on clips 34 and 36. A tab 136 with a pointed upper end is cutout of arm 132 and is bent upwardly to forcibly engage the upper housing cover in the same manner that portions 92 and 93 on clips 34 and 36 performed this function.

An alternate terminal construction is shown in FIG. 16 which is a typical view of the terminal end of a clip or collector bar as it projects through a suitable opening in a housing 10A. A leg 138 of a clip or terminal means is tapered similarly to portion 94 of clip 34, and a protuberance 140 forcibly engages at least one arcuate wall 142 of the opening 144 in the housing. Protuberance 140 serves to stabilize the leg 138 within the opening.

The device thus described can be easily assembled, for the collector bar 24, the clips 34 and 36, the resistor coil 28 and lead screw 26 are easily positioned and mounted in the manner described within the housing 10. This eicient drop in means of assembly is subsequently inalized by ultrasonically welding the cover 20 to the housing 10 to stabilize the components and to seal the top of the housing. Suit-able sealing agents can be used around the terminal tabs of the clips 34 and 36, and the collector bar 24 at the points where these terminals project from the housing. The lead screw is insulated from the operator by the nylon lead screw head 54, and the wiper assembly is protected against the overtravel by the unique ratcheting action of the wiper assembly 30 as the portions 74 and 76 thereof slide over the arcuate threads of the lead screw when the end walls of the housing are encountered.

Thus, frorn the foregoing, it is seen that the device of this invention will accomplish at least all of its stated objectives.

Some changes may be made in the construction and arrangement of our potentiometer without departing from the real spirit and purpose of our invention, and it is our intention to cover by our claims, -any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

We claim:

1. A miniature potentiometer, comprising,

a housing having an elongated chamber enclosed by top, bottom, two side and two end walls,

a resistance coil, collector member and lead screw in said chamber in substantially parallel relationship,

a Wiper member movably mounted on said lead screw and yieldably engaging said resistance coil and said collector member, and

a terminal member at each end of said resistance coil,

and a terminal member secured to said collector member, each of 4said terminal members being exposed on the exterior of said housing,

said collector member along its length including an upper, vertically disposed flat portion integral with a transversely inwardly and downwardly extending portion which merges into a ltransversely outwardly and downwardly extending portion.

2. The structure of claim 1 wherein a retainer wall extends in parallel relationship to said collector member and said collector member engages said retainer wall wherein said retainer wall serves to stabilize said co1- lector member.

3. The structure of claim 2 wherein a downwardly transversely inwardly extending portion is integrally provided on the lower longitudinal edge of said transversely outwardly and downwardly extending portion, said collector member being positioned adjacent `an exterior wall of said housing and means provided on the inside of said wall for engaging said collector member, said downwardly and outwardly extending portion engaging the upper end of said retainer wall, said collector member being pressfitted between said housing and said retainer wall and thereby tending to llatten out said lowermost portions of said collector member.

4. The structure of claim 3 wherein said terminal member of said collector member extends downwardly through the bottom of said housing and is integral with the lowermost portion of said collector bar.

5. The structure of claim 4 wherein said vertical portion of said collector member has at least one upwardly extending portion imbedded in a top wall of said housing.

6. A miniature potentiometer, comprising,

a housing having an elongated chamber enclosed by top, bottom, two side and two end walls,

a resistance coil, collector member and lead screw in said chamber in substantially parallel relationship,

a wiper member movably mounted on said lead screw and yieldably engaging said resistance coil and said collector member, and

a terminal member at each end of said resistance coil,

and a terminal member secured to said collector member, each of said terminal members being exposed on the exterior of said housing;

said wiper member including a pair of vertically spaced apart -arcuate shaped portions with -threads engaging said threaded lead screw, an integral U-shaped portion extending transversely of said lead screw and engaging said `collector member, the free ends of said U-shaped portion interconnecting adjacent ends of said arcuate portions.

7. The structure of claim 6 wherein said lead screw is positioned between said collector member and said resistance coil and above said resistance coil, and said arcuate shaped portions being positioned substantially on the top and bottom sides of said lead screw, said arcuate shaped portion on the bottom side of said lead screw having a portion extending transversely outwardly and downwardly for engagement with said resistance coil.

8. The structure of claim 7 wherein said terminal members at each end of said resistance coil each having a substantially semi-circular portion engaging said coil on its lower side and said portion of said wiper member engaging said coil being positioned on the top side thereof whereby said wiper member may move freely back and forth along said coil upon rotation of said lead screw.

9, A miniature potentiometer, comprising,

a housing having an elongated chamber enclosed by top, bottom, two side and two end walls,

a resistance coil, collector member and lead screw in said chamber in substantially parallel relationship,

a wiper member movably mounted on said lead screw and yieldably engaging said resistance coil and said collector member, and

a terminal member at each end of said resistance coil,

and a terminal member secured to said collector member, each of said terminal members being exposed on the exterior of said housing,

said terminal members at each end of said resistance coil each including a vertical portion with its upper end in engagement with the top of said housing and its lower end extending through an opening in the bottom of said housing and being press-fitted in said opening,

an arcuate-shaped portion extending inwardly from said vertical portion with the bottom portion of said arcuate-shaped portion resting on the bottom of said housing and the upper portion thereof being substantially open to receive said coil,

said wiper member engaging the upper portion of said coil to provide clearance between said wiper member and the arcuate-shaped portions of said terminal members.

10. A miniature potentiometer, comprising,

a housing having an elongated chamber enclosed by top bottom, two side and two end walls,

a resistance coil, collector member and lead screw in said chamber in substantially parallel relationship,

a wiper member movably mounted on said lead screw and yieldably engaging said resistance coil and said collector member, and

a terminal member at each end of said resistance coil, and a terminal member secured to said collector member, each of said terminal members being exposed on the exterior of said housing,

each of said terminal members at each end of said resistance coil including an arcuate shaped portion matingly engaging said coil along its lower side and a laterally outwardly extending portion extending from the outer edge of said arcuate portion, an integral downwardly extending portion extending from said outwardly extending portion and extending through the bottom wall of said housing,

said resistance coil terminal members each having an upstanding portion extending from said downwardly extending portion, said upwardly extending portion having a projection on its upper end imbedded in the top wall of said housing.

11. A miniature potentiometer, comprising,

a housing having an elongated chamber enclosed by top, bottom, two side and two end walls,

a resistance coil, collector member and lead screw in said chamber in substantially parallel relationship,

a wiper member movably mounted on said lead screw and yieldably engaging said resistance coil and said collector member, said wiper member being formed from unitary sheet material and having a central bight portion with opposite leg portions, said lead screw being received -in said bight portion, one of said leg portions engaging said collector member and the other leg portions being yieldably spring-loaded in an outward direction so that engagement with said collector member and said resistance coil yieldably urges said leg portions towards each other to insure rm engagement of the leg portions with said resistance coil and said collector member, respectively.

12. The structure of claim 11 wherein said lead screw is disposed above and between said collector member and between said lead screw member, and said leg portions of said wiper member extend downwardly and outwardly into engagement with the adjacent collector member and resistance member respectively.

13. The structure of claim 11 wherein said U-shaped wiper member has a pair of clamping fingers formed out of the center of said legs of said U-shaped member and extending laterally inwardly thereof from said bight portion, said lead screw being disposed in mating engagement with said pair of fingers, the bight portion of said leg portions being common to said fingers and, said lingers extending downwardly between said leg portions.

14. The structure of claim 1 wherein said leg portions are resilient so that if said wiper member engages an obstruction and is held against displacement on said lead screw, said leg portions will ex to permit the thread elements on said bight portion to ratchet over the arcuateshaped threads on said lead screw, one of said leg portions engaging said collector member and one of said leg portions engaging said resistance coil.

15. The structure of claim 1 wherein said terminal members include leg portions that extend through separate openings in said housing, said openings presenting an arcuate wall surface to guide said leg portions into said openings during assembly thereof, and a protuberance on said leg portion and engaging a wall surface within said opening to stabilize said leg element within said opening.

16. A miniature potentiometer, comprising,

a housing having an elongated chamber enclosed by top, bottom, two side and two end walls,

a resistance coil, collector member and lead screw in said chamber in substantially parallel relationship,

a wiper member movably mounted on said lead screw and yieldably engaging said resistance coil and said collector member, and

a terminal member at each end of said resistance coil, and a terminal member secured to said collector member, each of said terminal members being exposed on the exterior of said housing, said terminal members at each end of said resistance coil including a vertical portion with its lower end extending through an opening in the bottom of said housing and being press-fitted in said opening, the upper end of said vertical portion being bent upon itself to form a diagonally extending arm which terminated in an arcuate portion adjacent the bottom of said housing, said resistance coil being mounted in said arcuate portions, and means on the upper end of said terminal members engaging the top of said housing.

References Cited UNITED STATES PATENTS ROBERT K. SCHAEFFER, Primary Examiner.

H. HOHAUSER, Asssstant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,416,120 December 10, 1968 Robet P. Klug et al.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 8, line 8, claim reference numeral "1" should read Signed and sealed this 17th day of November 1970.

(SEAL) Attest:

Edward M. Fletcher, Ir.

Commissioner of Patents Attestng Officer WILLIAM E. SCHUYLER, JR. 

